Flow Void

Dr. Elster, I've been told you don't like or use the term 'flow void'. Why is that?

The term "flow void" is widely used among radiologists and others involved in MR imaging. It refers to the low signal seen in vessels that contain vigorously flowing blood and is generally synonymous with vascular patency. Flow voids can also be seen with active flow or pulsations of other fluids, like CSF or urine. The origin of the "flow void" signal loss is a combination of time-of-flight and spin-phase effects, described more completely in separate Q&A's.

Why don't I use the term or like it?It creates confusion for many non-radiologists.

Flow voids seen in the basilar and left internal carotid arteries consistent with vascular patency. No flow void is seen in the right internal carotid consistent with extremely slow flow or occlusion.

I believe that the fundamental purpose of an imaging report is to communicate clearly with the referring health care provider. Although radiologists, neurologists, neurosurgeons, and vascular surgeons are quite familiar with the term "flow void", many health care providers are not.

If you ask a random physician, nurse, or medical student unfamiliar with the details of MR imaging what a "flow void" means, you will likely receive an answer along the lines of "It means an absence of flow." This, of course, is exactly the opposite to the true meaning of the term.

So why use words in your report that are potentially confusing to your referring health care providers? Instead of saying, "A flow void is noted in the basilar artery," I dictate, "Normal flow-related signal loss is present in the basilar artery."